1. Field of the Invention
The invention relates to systems for feeding and transporting documents, to document hoppers used in these systems, and to adapting these systems for feeding envelopes and the like.
2. Background Art
A typical system for feeding and transporting documents includes a feeder in the document feeding portion of the system, and a series of roller pairs or belts in the document transporting portion of the system. In the feeding portion of the system, the feeder acts to separate and feed documents singly, in order, from a stack. In the transporting portion of the system, the roller pairs and/or belts convey the documents, one at a time, past other processing devices such as readers, printers, and sorters that perform operations on the documents. The feeder is typically a feed wheel, but may take other forms. Further, the components in the transporting portion of the system may take a variety of forms. An existing document feeder is shown in U.S. Pat. No. 6,199,854. That patent describes a document feeder with a variable speed separator.
In existing systems for feeding and transporting documents, operations that depend on the position of the document are generally performed in the transport stage, or transporting portion of the system. For example, U.S. Pat. No. 5,848,784 describes a document separation apparatus. That patent describes the downstream acceleration/deceleration of documents with pinch rollers to adjust document spacing. U.S. Pat. Nos. 5,419,546; 5,437,375; 5,439,506; 5,509,648; 5,671,919; and 5,908,191 describe examples of other document operations.
As modern document handling devices are typically fitted with an automatic feeder mechanism to singly introduce documents into a track for further processing, a hopper is usually associated with the feeder so that the machine can load a number of documents to be processed. As feed rates increase, and feed mechanism reliability improves, there are advantages to making hopper capacity larger.
The difficulty with making hopper capacity larger is one of consistency. Document feeders need to have a supply of documents presented to the feeding mechanism in a consistent manner. This is a task of the document hopper. The variety of documents used in different applications make such consistent presentation difficult.
There is an ideal set of forces for feeding a document in a given feeder. The closer each document can be to this ideal set of forces, the better feeder performance will be. More specifically, the feeder must apply enough pinch force to allow the document to feed, but not so much as to result in the tearing apart of the document during feeding. As hopper capacity is increased, the variation in force against the stack between that needed to move a full hopper of documents and that needed to move the last few documents and provide an acceptable force to the document being fed is increased.
Typically, some form of mechanical intervention urges the document stack along in the hopper. An existing form of mechanical intervention used to urge the document stack along in the hopper toward the feeding mechanism applies a force to the document stack with a flag. Various approaches have been taken for driving the flag to produce the flag force or flag weight against the document stack.
Additional background information may be found in U.S. Pat. Nos. 6,474,637; 6,417,221; and 6,260,841.
Document processing systems are normally built to handle single thickness items, one at a time. Considerable effort (for example, double document detectors) goes into ensuring that only one thickness of paper is fed at a time. Further, a stack of single thickness items tends to be firm, and of consistent dimension.
In certain applications, it would be desirable to process envelopes in a document processing system. For example, automatic teller machine (ATM) envelopes could be imaged by the document processing system to capture information therefrom. In this way, it would not be necessary to copy the information from the envelopes to additional documents.
However, envelope stacks (for example, a stack of ATM envelopes) are spongy. This is due to the folded nature of the envelope construction. More specifically, the folded nature of the envelope construction changes the thickness of an envelope depending on location, and entrains air in the envelope stack because the folds are not of zero radius. Accordingly, envelope stacks are only processed with limited performance due to the fact that document processing systems are normally built to handle single thickness items.
For the foregoing reasons, there is a need for an improved system for feeding and transporting documents that is capable of feeding envelopes and the like with improved performance.